Dental implants are used to replace missing or badly damaged teeth. In order to mount a dental implant securely in bony tissue, a hole must be drilled into supporting bone structure, such as into the mandibular or maxillary jaw bone of the patient. The implant portion that holds the artificial tooth is usually made of titanium or a titanium alloy and must be able to rapidly integrate with the bone of the patient. Once the implant is properly seated and secure, the artificial tooth can be installed.
Osteotomy and related procedures in which a hole is drilled into the maxillary or mandibular jaw bone at the proper angle and dimension, requires a good degree of accuracy, so that the implant fits correctly without damage to surrounding tissue or structures and so that the completed work is aesthetically acceptable. For edentulous or at least partially edentulous patients, implant planning is carefully executed. Based on information from x-ray or computerized tomography (CT) imaging of the patient's dental arch, dedicated software tools allow the dentist to define the location, diameter, length or drill depth, shape and angulation of the implant to be affixed on the patient's jaw bone. One consideration in this planning is reducing the risk of damage to nearby nerves or blood vessels.
One appliance that is used to assist in implant preparation is the surgical guide. Custom-fabricated for each patient, shaped to conform to at least a portion of the patient's dental arch, the surgical guide must be fitted to the patient's mouth and should include one or more guide holes to guide the dental drill into the supporting bone according to the implant planning.
The surgical guide used for this purpose can be fabricated as a plastic appliance using a stereolithographic process or by a milling process, based on the digital data obtained during implant planning. Some dental sites are equipped with a 4-axis milling machine for dental prostheses, enabling the surgical guide to be prepared on-site. Though 5-axis milling equipment is available, the 4-axis milling machine is capable for use with other dental prostheses including for milling a surgical guide. There are limitations to 4-axis devices for forming surgical guides having suitable characteristics for some types of procedure.
In addition to providing the capability for straightforward fabrication, there are a number of other challenges for designing a surgical guide that facilitates osteotomy and related drilling procedures. Size is one consideration; the guide should be sizable enough to provide stability for the rotating drill, but should not be uncomfortable for the patient. The guide should be formed from a suitably durable, non-toxic material. The design for a surgical guide should register readily in the mouth of the patient, so that the drill location and angle are precisely controlled and can be customized for the particular patient.
Thus there is need for a surgical guide that is easy to use, that can be readily fabricated using less expensive equipment and customized for an individual patient, that can be designed for use with specialized software for implant planning, and that has reduced cost over more complex drill guide alternatives.